Science is uncovering ever more new and interesting findings about non-human species and it would seem that much of lay mis-understanding of the differences between human and non-human species are driven by prejudice and speciscism without much interaction with the species concerned. The following is not an exhaustive list of the differences/similarities but questions raised in my mind for some time now along similar lines to the OP which I would like to see a discussion. Please ensure that the points you raise has a logical basis back to empirically observed and documented studies of differences/similarities between human and non-human species, not bald statements which only serve to highlight one’s non-relationship with scientific facts.
(1) Humans are not the only species with theory of mind: so do the other great apes and dolphins etc. Together with the theory of mind would be the ability of deceive and individual apes have been observed to do so. Would this therefore mean the ability to sin? And if so would there be a requirement to confess sins and seek redemption?
(2) Scientists have placed chimpanzees as generally capable of achieving the intellectual age of 6 (of a human child). Many of those who have interacted with chimpanzees would think of a higher equivalent age than 6. If we send our 6-year-olds to Sunday School, would we need to send chimpanzees to Sunday School, assuming they have mastered human language communication (e.g…, in a similar fashion to Koko)? After such suitable instructions, would we be required to baptise such chimpanzees and then to First Holy Communion? If it can be proven that such species are incapable of reaching the intellectual age for confirmation, would this fact have a bearing on the decision to baptise the individual? If so, would this mean that baptism in the Oriental Rite is possible (as confirmation & Holy Communion follows immediately from baptism) but not in the Latin Rite?
(3) Recent findings in the Rising Star cave in South Africa indicate a new pre-human species of Homo Naledi 1-2million years old, which seem to be burying their dead. More incontrovertibly, homo neanderthals 24-600,000 years ago, are known to bury their dead, often with valued objects. This indicate a capacity for understanding of the afterlife. Would such capacity mean that evangelisation is not limited to our species? If so, would it mean that the fullness of the catechism apply before baptism can be administered or is there a requirement to assess how far the capability of understanding by the other species extend and only that part of the catechism and canon law that the other species is capable of understanding applies?
(4) A fundamental part of being human involves a certain level of self awareness, including the Theory of Mind. Would the criteria of having a spirit (as opposed to a soul) have a similar criteria since it was originally deemed that only a human can have a spirit. Yet, elements of being human and self-awareness is more a continuous spectrum rather than a discrete definition. So, would an individual or a species need to reach a particular tipping point at which it will then obtain a full spirit identical to one held by a member of the human species or does it have a mix of spirit and soul characteristics in line with its level of self-awareness/etc. If so, would this mean that different species could have different mix of soul-spirit? Also, if so, would this mean different human individuals have similarly different mix of soul-spirit?
My intention here is to avoid a dogmatic discussion of the philosophy of souls and spirits divorced from recent scientific findings. I would like the answer to be fully informed by scientific understanding.